1. Field of the Invention
The present invention relates to portable tools for machining the end of a pipe or tube workpiece for enabling subsequent welding of the workpiece. Such tools are commonly referred to in the welding field as pipe or tube end preparation tools.
2. Description of the Prior Art
Portable tube end preparation tools are generally well-known in the prior art, and are exemplified in U.S. Pat. Nos. 3,051,059, 3,131,599, 3,228,268, and 4,319,503.
In such prior art systems, the cutter head of the tool carries the tool bits and is rotatable about the longitudinal axis or other cutting axis of the tool. The cutter head is driven by a drive shaft arrangement that usually is supported within the tool housing by a bearing or the like that may simply be comprised of a sliding bearing surface on the inside of the housing against which the cutter head drive shaft rotates. While rolling or ball-type bearings are also utilized to support drive shafts, such bearings are rather conventionally used without regard to the objective of reducing the size or weight of the drive shaft assembly or reducing the overall size of the tool housing. Moreover, in accordance with prior art applications, since thrust and radial loads from the cutter head must be reacted into the tool housing through the drive shaft, the various drive line parts must be constructed quite ruggedly to withstand the rigors of repeated and continuous machining operations under severe operating conditions. Consequently, the overall size of such portable pipe end preparation tools must be adequate to accommodate the rugged drive line components and the components themselves must be designed to withstand the stress loads that are expected to be encountered during the operational life of the tool. Any desired downsizing of the portable tool, as well as weight savings desired to be effected, tends to be limited by the apparent need to provide rather large and massive drive components and bearing surfaces for the rotating drive line parts within the tool.
The present invention is concerned with a drive shaft assembly for a portable tube end preparation tool that overcomes the problems associated with prior art tools of the type described above.